#include<stdio.h>
int main()
{
	int i = 1;
	double sum = 0;
	int flag = 1;
	for (i = 1; i <= 100; i++)
	{
		sum = sum + flag * (1.0 / i);
		flag = -flag;
	}
	printf("%lf\n", sum);
	return 0;
}